BRPI0721181A2 - heat and wind protection for the building - Google Patents

Abstract

The “heat- and wind-screen for the building industry” is an original and economical concept that increases comfort inside buildings subject to strong solar radiation. It comprises cladding the roof and/or the walls with perforated metal sheets and using spacers having an original design and disposition. The investment is low due to the proposed mounting mode and the low cost of the materials used. Savings can then be achieved by reducing the energy consumption for the air-conditioning of the building. The structure of the “heat- and wind screen for the building industry” induces important load losses for the winds on their path about the building and the building it covers exhibits a better resistance to strong winds. The “description” section successively contains the description of the device, the physical properties used, the performance measured on a model and an experimental house, a mounting technique, and a proposal for modelling the action of winds in order to justify the care to be taken when finishing the mounting of ridge tiles.

Description

Patent Invention Descriptive Report

"HEAT AND WIND PROTECTION FOR CONSTRUCTION."

Application domain:

Construction and public works

Technical Domain:

Energy saving and control

Protection of building roofs against violent winds.

10

Technical problems

Rooftops exposed to strong solar shocks store energy in the form of heat and radiation in large quantities inside buildings.

Roofs exposed to violent winds suffer mechanical stress

considerable losses that can lead to their

Solution offered

Duplication of roofs and vertical walls with the aid of perforated sheets. Various types of perforated sheets having holes of different diameters can be used as desired (see "2-1 Physical Properties Used").

Benefits:

Protection improves habitat comfort in very sunny areas, saves energy on the use of air conditioners and this, with a low investment due to the low cost of materials used, makes the habitat safer in case of exposure to violent winds. .

Description Summary:

1. Presentation 2. Performances

2-1 The Physical Properties Used

2-2 Some highlights of measurements made on a mockup and on the experimental house. 3. Example of retractors and protection mounting

3-1 The Spacers

3-2 Mounting the Guard

4. Wind action over protection 4-1 wind side

4-2 side under the wind

5. Conclusion

1. Presentation

The protection consists of the duplication of the existing roof by plates

pre-lacquered and perforated galvanized (Figure 1, see summary). Shortly before installation, these sheets undergo cold rolling profiling similar to that of full sheets intended for cover and transport by means of a pad.

Forging is intended to give the sheet metal sufficient rigidity

to withstand different mechanical stresses such as their own weight, that of the assemblers, the wind stresses, if any, that of snow, etc.

Mounting is particularly well suited to sheet metal roofs, as in this case it is supported by spacers which are fixed at the level of the old roof sheet fixings, so that no additional preparation is required.

These perforated sheets are found on the market, whose current destination is mainly transport by means of pad.

In the following, a comparison of the performances of two types of perforated sheet will be given by way of illustration, but any type of perforated sheet may be suitable for heat and wind protection.

The following are also detailed elements for defining roof protection, but these elements also refer to the much easier wall mounting (see details at the end of paragraph 3-2).

2. Performances

2-1. The Physical Properties Applied By calm weather, or downwind side of a roof, since a perforated sheet is illuminated by the sun (Figure 2), a temperature difference appears between the air layer in contact with the sheet, the lighted side, and the surrounding air layers. Heated air less dense than cold air rises from the effect of Archimedes and dilutes into the ambient atmosphere away from the plate.

This mechanism produces a continuous suction of air under the plate that passes through the perforations and in turn heats up. Air plays a role of heat-carrying fluid that exchanges heat with the plate circulating in its contact.

As a result, the plate temperature is kept close to

that of the ambient air temperature. However, perforated plate temperatures were measured that could go up to 80 ° C above ambient temperature side under the wind of each experimental.

The primitive roof under the perforated plate receives very little

energy in the form of infrared radiation from the perforated plate. It receives mainly the energy from solar radiation that passes through the holes. The heat transmitted by this diffuse radiation throughout the old roof leads to a moderate rise in its temperature. When it is dark in color the temperature of the old roof remains next to the temperature

of the perforated plates. When it is light in color, its temperature may be

lower, up to two degrees below.

For moderate wind time (speeds below 15 m / s), a velocity gradient in air flow is observed. This settles from low to higher as it moves away from the roof.

The air velocity is thus higher on the upper face of the perforated plates than on its lower face. This speed gradient results in a natural air intake between the roof and the perforated plate through the perforations. It is the Bernoulli effect that explains this phenomenon: in a subsonic flowing fluid, an increase in velocity is accompanied by a

pressure decrease.

This phenomenon makes the perforated plate cooling even more effective. Two species of plates were tested are shown in Figure 3 on scale 1. The choice of a type of plate should be guided by the protection to be privileged:

- if wind protection is less urgent, as is the case in Guyana, plates with small perforations will be chosen as they

better protection and best protection for heat protection.For example with Type A sheets (figure 3a), the covered surface is 85.5% of the total surface, ie only 14.5% of the surface. from the old roof it still receives the sun's rays;

- With Type B sheets (Figure 3b0, there is only 77.3% of the roof in the shade, ie the remaining sunlit surface is 22.7% of the

total roof surface. The old roof receives more heat, on the contrary, the holes are larger, in case of big wind, the pressure losses suffered by the wind are more considerable, which reduces the risk of the roof assembly being torn off. 2-2. Measurements made on a mockup and on the experimental house

Two types of structure were used to test the performance of "heat and wind protection for construction". An experimental house, shown in the photo in figure 4, and a model presented in detail with the help of figures 5, 6 and 7. The model object was to verify the opportunity to develop a device such as "heat and heat protection". wind". It has indeed made it possible to highlight interesting performances in the field of heat protection. But she also showed her limits due to her small size. The experimental house allowed to confirm the results obtained with the model. In addition, it has also allowed to reveal the clearest way of only perceptible phenomena about the model, such as temperature gradients along the plates.

Figure 5: Definition views of the scale model from 3.5 cm to 1 m.

Figure 6: Measurement point positions and designation of measured temperatures.

Figure 7: Photos of the model with and without protection.

The model was made of 12 mm thick laminated wood. The wood was then tarred to resist ambient humidity and insects. The base cover was made with the aid of a pre-lacquered navy blue plate.

This put this model in the worst possible conditions in the face of radiation.

The clearance d between bottom plate and top plate could range from 80 to

300 mm thanks to an adapted device visible in the picture in figure 7a. Figure 6 makes it possible to schematically mark where the temperatures have been highlighted and this in three configurations: without protection (Figure 6a) 'with a protection by a plate full of sky blue color (Figure 6b),

protected by a type A perforated plate (figure 6c). Table 1 presents an extract from the field of temperature measurements made on the model and the experimental house during the "small summer of March" of 2006. These are really high temperatures, not averages.

The table rows correspond to a highlight of the same day temperatures between 11 am and 12:30 pm. For each row, sunny day and wind conditions are roughly identical. For winds, the average velocity was between 5 and 6 m / s, with gusts up to 10 m / s for approximately 5 to 10 seconds but spaced 2 to 15 minutes.

The faces on which the temperatures were highlighted are oriented towards the prevailing winds: full East for the model and East, Northeast for the experimental house. In the "highlighted" column Mq designates the model, and M E designates the house.

experimental.

In the "status" column, the protection status can be read: TN uncovered roof B P1 full plate protection Perfo perforated plate protection Type A for the model and type B for the

experimental house.

Column "d (mm)" reports deviations between protection and old roof in millimeters. Note: To make the link between Figure 6 and Table 1, you must replace the letter d with the Greek letter delta in the table. Similarly it should be read theta.

Table 1: Highlighted temperatures March 2006.

Highlights State d (mm) Qa qi qS2 qS3 qS4 qS5 qS6 qib qSq qic qsc Mq TN 29 ==== ==== === 44 44.5 45 34 37.5 35 38.5 Mq B P1 80 31.5 38 38.5 39 32 33 32 32.5 34 34 35 Mq B P1 200 31.5 34.6 35.5 36 31 32 32 31.5 33 31.5 33 Mq Pe 80 31.5 31, 9 32 32.3 32.9 33 30 30.5 33 32.5 34 Rfo Mq Per rfo 200 31.2 29.9 30 30.2 30.6 31.5 32 30 33 31 33.5 ME TN == === 28 === === === 62 62 62 38 42 45 62 ME B P1 175 30,5 43 47 45 39 42 40 30,5 31,5 33 33,5 ME Per 175 175,5 33 32 32 32.5 32 32 29.7 31 32.5 33

Temperatures in degrees Celsius are designated by the letter q.

In column qa it was brought to the highlighted room temperature with a mercury thermometer (accuracy 0.1 ° C).

The measurement of qa was made in a dark area and sheltered from the wind.

The index (i) indicates that the temperature was measured inside the model (approximately 200 mm from the wall) or the experimental house (in the core of the piece), with the aid of the mercury thermometer.

The index (s) indicates a surface temperature measured with the aid of an infrared thermometer accurate to 0.5 0C1 to account for the dispersion of measurements near a point. Index (b) designates the bottom of the model or a part (not

located on the first floor of the experimental house and

The index designates to fill in the mockup or the experimental house (ie, the volume located directly under the plate).

Table 1 allows you to compare different protection configurations with the unprotected roof. Highlights on the model show the effectiveness of ventilation on a small surface (even without protection).

For the experimental house, unprotected plate temperatures reach tops: 62 ° C windswept and up to 75 ° C downwind (West Side). The deviation between the old cover and the protection plate also plays a role, but interesting performances are noted from the smallest spacing (80 mm). On the contrary, it is useless to increase this distance indefinitely, since beyond 200 mm there is no further improvement in thermal performance. On the contrary, more important clearances can be considered for protection against the great winds.

For the experimental house, a 175 mm d (delta) offset was chosen to consider the results obtained on the model. It will be noted the small gap between the ambient temperature and the temperature of the perforated plate (last line of the table), which demonstrates the effectiveness of the protection in this configuration.

3- Examples of spacer and protection assembly.

3-1 The spacers

The scheme of figure 8 defines a spacer of the type used for the experimental house. For mounting facilities, it is recommended to have a spacer facing downwards.

The spacers must be adapted to the type of roofing sheet to be duplicated. Therefore, the common characteristics (dimensions fixed in figure 8 (, the common properties (described below) and variable dimensions of one type of sheet to be covered with the other) (dimensions a mainly, b and c figure 8) will be noted.

Properties common to all spacers:

For reasons of strength, the flap 2-flap 3 assembly should be as close as possible to the top of a corrugation of the sheet to be covered.

For sheets that have flat top corrugations (Figures 8 and 9a), this condition is easy to accomplish. Just make sure that the dimension (a) is equal to or more than 10 mm maximum the distance between the outer folds of two successive undulations (10 mm to be split between the two ends).

For plates having rounded top corrugations (Figures 9b and 9c), the dimension (a) shall exceed 15-20 mm (maximum and dividing between the two ends of the spacer) the distance between the axes of two successive tops.

If this condition is not respected, there is a risk of bending under load the base of the spacer. The explanation is that the fastening screws must imperatively pass through the tops of these undulations, and that a place must be kept inside the spacer to insert the wrench and must be used to tighten these screws.

It will be noted. However, for the so-called "corrugated sheets" it is possible to match the undulation of the corrugation with the edges of the spacer (with a possible overrun of 5 m, figure 9c).

The dimension (s) will then be chosen such that the spacer covers several undulations having a length of 300 mm or more. For each end of the spacer, a setscrew will be placed at the level of the curl top closest to that end.

The second variable dimension is dimension (b). This depends on the type of protection considered. The highlighted in Table 1 showed that the protection is already effective with a spacing of 80 mm between plates. The corresponding spacer will have greater mechanical strength. For the experimental house the 175 mm clearance was obtained with a

dimension b = 150 mm to which the undulation height of 25 mm is added.

A finite element calculation has shown that the spacer for which b = 150 mm resists flexion and scorching, in cases where it does not exceed the effort F in the configuration of figure 10. The calculation indicates that the limit value of this effort when it is arranged

parallel to the roof and oriented downwards (figure 10) is 1800 Newtons. The most requested zone is that of tabs 2 and 3.

Such a high load can be achieved when mounting by the effect of the weight of the assembler himself. It is also wise to advise assemblers not to lean on the top of a spacer during

assembly operations.

Naturally, the higher the elevation (b), the more the spacer risks bending under the load. For values of (b) over 150 mm, it is recommended to increase the dimension (c) of the spacer base and to add a

second rivet above the first (figure 11).

The series of photos in figure 12 shows the different steps of making a spacer on the flowerbed by the assembler craftsman. The example shown leads to the manufacture of a house spacer proof: (a) cut in a U-shape (60 mm; 150 mm; 35 mm) of a length of 430 mm;

(b) clipping of tabs 1, 2 and 3;

(c) folding flaps 1 outwardly of the U-profile;

(d) folding tabs 2 into the U-profile;

(e) folding tabs 3 so that it covers tabs 2;

(f) placing the rivet for the connection of tabs 2 and 3 (the rivet head must be inside the spacer to allow mounting bolt mounting);

(g) placement of spacer over roof. The spacer should be

just above the beam where the roof plate was fixed. If possible, use the existing holes and be sure to place a rubber washer between the plate and the spacer to ensure tightness;

(h) placement of the set screw. Using a paper shim

The tarmac, placed on the spacer and the plate, allows to harden the base of the spacer, but is not required;

(i) the spacer is ready to receive the 30 X 50 mm rectangular section bracket onto which the perforated plate of the guard itself will be fixed.

3-2 Mounting the Guard

The distance separating two successive spacers may be approximately one and a half times the dimension (a) in Figure 8. The length of 300 mm may be increased and even doubled, without affecting the strength of the assembly in the few geographical areas. exposed to violent winds. This will be controlled so that the distance between two spacers is less than or equal to dimension (a). Once the spacer is placed over the old roof, it receives the bracket that fits into the upper part (figure 13a). Previously, the substrate received a fungicidal treatment and was entirely covered by a tarred aluminum foil (roofing seal-like film). The purpose of this film is to protect the substrate from insect attack and moisture. Simple clamping of the spacer allows the support to be maintained during assembly, but such maintenance can also be enhanced with the aid of a temporary adhesive film visible in Figure 13b.

It is best to avoid fixing the bracket with the help of screws placed on its top, because the screw heads risk scratching the organic coating under the perforated plate during its placement.

After placement, the perforated sheet is fixed with the aid of short, classic roof screws (galvanized bottom strip, diameter 6 mm and 40 mm under head). It is these screws that ensure the support / spacer connection and the perforated plate / support connection.

A properly placed screw must pass through the perforated plate and the top of the spacer before being inserted into the bracket.

To limit the surface of the bolts in contact with rainwater, it is preferable to place these bolts on the undulating bottom of the perforated sheet metal profile (figure 13b).

To facilitate assembly, it is preferable to use lubricated screws (with the aid of tire grease, for example).

For wall protection, the fabrication and mounting of the spacers is similar to those of Figures 12 and 13, and the spacers and their brackets will be arranged simply on 1.20 m spaced horizontal lines. These spacers may have a dimension (Figure 8) fixed at 300 mm and a horizontal space of 600 mm shall be respected between two consecutive spacers. The perforated plates shall be fixed so that there is a gap of at least 300 mm between the base of the plate and the ground. To fix a limiting size of the perforated sheets for the wall guards, the height reached by the sheets can be limited so that their tops, when mounted, penetrate exactly into the shade zone projected by the roof at 9 o'clock in the morning east side and 17 hours west side. In this way the effectiveness of the device will not be affected, but for aesthetic reasons one can also adopt the larger dimensions. However, a clearance of at least 300 mm shall be maintained between the sheet top and the underside of the roof to allow good air circulation in the space between wall and sheet.

4- Wind action over the protection The most unfavorable winds are those that have a strong component in a direction perpendicular to the lower edge of the roof. The most exposed roofs in this case are the roofs with two slopes. When the wind is oriented parallel to the roof, it generates relatively uniform pressures on the entire roof. The pressure losses caused by the perforated sheets decrease the flow velocities, which, compared to a classic roof, leads to a decrease in the pressure gap between the interior of the building and the exterior of the roof. The following two paragraphs are therefore devoted to roofs with two slopes exposed to winds perpendicular to the ridge edge. 4-1 wind side

It is the most mechanically requested roof face. In the vicinity of the roof, side by side in the wind, the wind's current lines slope towards the slope (figure 14). This is followed by a pressure gradient growing as it moves away from the center of curvature (deduced relationship from Bernoulli's theorem), that is, as it approaches the plate. At the same time, velocities are distributed along a gradient that varies in the opposite direction. Thus, two phenomena coexist near the protection: at its base, air spreads over the perforated plates, passing through the holes and between the spacers, which causes large pressure losses, and a sharp decrease in air velocities under the perforated plates. As a guide, with winds of 10 m / s, a 3 to 4 m / s draft was measured using a hot wire anemometer under the perforated plate of the model.

Higher on the structure, speeds are higher on the

upper face of the perforated plates which on its lower face. This is followed by a suction of the air fillets circulating under the underside and the existence of depression zones at the very top of each sheet perforation (Figure 15).

These mechanisms have effects that tend to offset each other: there are

a winding action on the base of the guard and a suction effect that decreases the topping effect. Globally, the presence of the shield slows down the velocities of air flowing over the roof.

In relation to an unprotected structure, the result is that the protection produces a decrease in the pressure clearance between the interior and exterior of the house.

4-2 side under the wind

The zone under the wind, relatively calm in relation to the previous one, is a zone of almost uniform low pressures. The cylinders generated by the roof top passage can even have a placement effect by bending the air over the roof. This effect is all the more marked the stronger the wind pains.

The lowest pressures are reached in the vicinity of the ridge because of the air circulating under the perforated plates.

To sum up, in case of exposure to violent winds, the areas most exposed to low pressure are located near the roof ridge. To reinforce the protection of the protection in these zones, it is therefore

The distance between the spacers on the nearest ridge beam must be reduced as much as possible.

In addition, the perforated sheet in the ridge paper and the other sheets which make the connection between two tabs of the shield must have free edges (figure 16), ie without folding.

The connection of these ridges with the plates of the protection body shall be made with the aid of rivets (diameter 5 mm for type A plates, diameter 6 mm for type B plates), and at a ratio of at least an edge rivet, as shown by the distribution of rivets over the protection of the experimental house visible in the picture in figure 16.

5- Conclusion

"Heat and wind protection for the building" improves comfort inside the buildings it covers, lowering the roof temperature and allowing a more homogeneous temperature in the different parts. This naturally induces the energy savings used for air conditioning.

Slowing down the wind speed in direct contact with it, it reinforces the resistance of the building in case of violent wind. It should be noted that ridges also play a major role in reducing the risk of wind blasting at roof top level.

Claims (3)

"HEAT AND WIND PROTECTION FOR CONSTRUCTION." 1. Duplication of roofs and vertical walls of buildings characterized by the use of perforated plates for the rapid and total elimination of solar heating radiation towards the building. Duplication according to Claim 1, characterized in that it is carried out with the aid of spacers whose dimensions, design and arrangement on the old roof or on the wall depend essentially on these spacers and their correct mounting. 3. Building wind protection process characterized by the steps of: a) including objects with large areas such as spacers and perforated steel blades for energy reduction; and b) stiffening of the roof through a beehive effect produced by the spacers, with sealing on its perimeter.